267 lines
10 KiB
Python
267 lines
10 KiB
Python
import json
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import time
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import warnings
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from collections import Iterable
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from channels import Channel, Group
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from channels.asgi import get_channel_layer
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from channels.auth import channel_session_user, channel_session_user_from_http
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from django.apps import apps
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from django.core.exceptions import ObjectDoesNotExist
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from django.db import transaction
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from ..core.config import config
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from ..core.models import Projector
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from .auth import has_perm, user_to_collection_user
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from .cache import websocket_user_cache
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from .collection import Collection, CollectionElement, CollectionElementList
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def send_or_wait(send_func, *args, **kwargs):
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"""
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Wrapper for channels' send() method.
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If the method send() raises ChannelFull exception the worker waits for 20
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milliseconds and tries again. After 5 secondes it gives up, drops the
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channel message and writes a warning to stderr.
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Django channels' consumer atomicity feature is disabled.
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"""
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kwargs['immediately'] = True
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for i in range(250):
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try:
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send_func(*args, **kwargs)
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except get_channel_layer().ChannelFull:
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time.sleep(0.02)
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else:
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break
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else:
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warnings.warn(
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'Channel layer is full. Channel message dropped.',
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RuntimeWarning
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)
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@channel_session_user_from_http
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def ws_add_site(message):
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"""
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Adds the websocket connection to a group specific to the connecting user.
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The group with the name 'user-None' stands for all anonymous users.
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Send all "startup-data" through the connection.
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"""
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Group('site').add(message.reply_channel)
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message.channel_session['user_id'] = message.user.id
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# Saves the reply channel to the user. Uses 0 for anonymous users.
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websocket_user_cache.add(message.user.id or 0, message.reply_channel.name)
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# Collect all elements that shoud be send to the client when the websocket
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# connection is established
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output = []
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for app in apps.get_app_configs():
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try:
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# Get the method get_startup_elements() from an app.
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# This method has to return an iterable of Collection objects.
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get_startup_elements = app.get_startup_elements
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except AttributeError:
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# Skip apps that do not implement get_startup_elements
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continue
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for collection in get_startup_elements():
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user = user_to_collection_user(message.user.id)
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output.extend(collection.as_autoupdate_for_user(user))
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# Send all data. If there is no data, then only accept the connection
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if output:
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send_or_wait(message.reply_channel.send, {'text': json.dumps(output)})
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else:
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send_or_wait(message.reply_channel.send, {'accept': True})
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@channel_session_user
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def ws_disconnect_site(message):
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"""
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This function is called, when a client on the site disconnects.
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"""
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Group('site').discard(message.reply_channel)
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websocket_user_cache.remove(message.user.id or 0, message.reply_channel.name)
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@channel_session_user_from_http
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def ws_add_projector(message, projector_id):
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"""
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Adds the websocket connection to a group specific to the projector with the given id.
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Also sends all data that are shown on the projector.
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"""
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user = message.user.id
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if not has_perm(user, 'core.can_see_projector'):
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send_or_wait(message.reply_channel.send, {'text': 'No permissions to see this projector.'})
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else:
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try:
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projector = Projector.objects.get(pk=projector_id)
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except Projector.DoesNotExist:
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send_or_wait(message.reply_channel.send, {'text': 'The projector {} does not exist.'.format(projector_id)})
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else:
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# At first, the client is added to the projector group, so it is
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# informed if the data change.
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Group('projector-{}'.format(projector_id)).add(message.reply_channel)
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# Then it is also added to the global projector group which is
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# used for broadcasting data.
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Group('projector-all').add(message.reply_channel)
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# Now check whether broadcast is active at the moment. If yes,
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# change the local projector variable.
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if config['projector_broadcast'] > 0:
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projector = Projector.objects.get(pk=config['projector_broadcast'])
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# Collect all elements that are on the projector.
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output = []
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for requirement in projector.get_all_requirements():
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required_collection_element = CollectionElement.from_instance(requirement)
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output.append(required_collection_element.as_autoupdate_for_projector())
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# Collect all config elements.
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collection = Collection(config.get_collection_string())
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output.extend(collection.as_autoupdate_for_projector())
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# Collect the projector instance.
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collection_element = CollectionElement.from_instance(projector)
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output.append(collection_element.as_autoupdate_for_projector())
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# Send all the data that were only collected before.
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send_or_wait(message.reply_channel.send, {'text': json.dumps(output)})
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def ws_disconnect_projector(message, projector_id):
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"""
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This function is called, when a client on the projector disconnects.
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"""
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Group('projector-{}'.format(projector_id)).discard(message.reply_channel)
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def send_data(message):
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"""
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Informs all site users and projector clients about changed data.
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"""
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collection_elements = CollectionElementList.from_channels_message(message)
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for user_id, channel_names in websocket_user_cache.get_all().items():
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if not user_id:
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# Anonymous user
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user = None
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else:
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try:
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user = CollectionElement.from_values('users/user', user_id)
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except ObjectDoesNotExist:
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# The user does not exist. Skip him/her.
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continue
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output = collection_elements.as_autoupdate_for_user(user)
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for channel_name in channel_names:
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send_or_wait(Channel(channel_name).send, {'text': json.dumps(output)})
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# Check whether broadcast is active at the moment and set the local
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# projector queryset.
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if config['projector_broadcast'] > 0:
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queryset = Projector.objects.filter(pk=config['projector_broadcast'])
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else:
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queryset = Projector.objects.all()
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# Loop over all projectors and send data that they need.
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for projector in queryset:
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output = []
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for collection_element in collection_elements:
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if collection_element.is_deleted():
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output.append(collection_element.as_autoupdate_for_projector())
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else:
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for element in projector.get_collection_elements_required_for_this(collection_element):
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output.append(element.as_autoupdate_for_projector())
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if output:
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if config['projector_broadcast'] > 0:
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send_or_wait(
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Group('projector-all').send,
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{'text': json.dumps(output)})
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else:
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send_or_wait(
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Group('projector-{}'.format(projector.pk)).send,
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{'text': json.dumps(output)})
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def inform_changed_data(instances, information=None):
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"""
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Informs the autoupdate system and the caching system about the creation or
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update of an element.
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The argument instances can be one instance or an interable over instances.
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"""
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root_instances = set()
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if not isinstance(instances, Iterable):
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# Make sure instances is an iterable
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instances = (instances, )
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for instance in instances:
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try:
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root_instances.add(instance.get_root_rest_element())
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except AttributeError:
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# Instance has no method get_root_rest_element. Just ignore it.
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pass
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# Generates an collection element list for the root_instances.
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collection_elements = CollectionElementList()
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for root_instance in root_instances:
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collection_elements.append(
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CollectionElement.from_instance(
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root_instance,
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information=information))
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# If currently there is an open database transaction, then the
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# send_autoupdate function is only called, when the transaction is
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# commited. If there is currently no transaction, then the function
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# is called immediately.
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transaction.on_commit(lambda: send_autoupdate(collection_elements))
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def inform_deleted_data(*args, information=None):
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"""
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Informs the autoupdate system and the caching system about the deletion of
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elements.
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The function has to be called with the attributes collection_string and id.
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Multible elements can be used. For example:
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inform_deleted_data('motions/motion', 1, 'assignments/assignment', 5)
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The argument information is added to each collection element.
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"""
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if len(args) % 2 or not args:
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raise ValueError(
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"inform_deleted_data has to be called with the same number of "
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"collection strings and ids. It has to be at least one collection "
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"string and one id.")
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# Go through each pair of collection_string and id and generate a collection
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# element from it.
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collection_elements = CollectionElementList()
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for index in range(0, len(args), 2):
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collection_elements.append(CollectionElement.from_values(
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collection_string=args[index],
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id=args[index + 1],
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deleted=True,
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information=information))
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# If currently there is an open database transaction, then the
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# send_autoupdate function is only called, when the transaction is
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# commited. If there is currently no transaction, then the function
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# is called immediately.
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transaction.on_commit(lambda: send_autoupdate(collection_elements))
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def send_autoupdate(collection_elements):
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"""
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Helper function, that sends collection_elements through a channel to the
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autoupdate system.
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Does nothing if collection_elements is empty.
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"""
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if collection_elements:
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send_or_wait(
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Channel('autoupdate.send_data').send,
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collection_elements.as_channels_message())
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